This invention generally relates to a gas turbine engine, and more particularly to a gas turbine engine having a variable shape inlet section.
In an aircraft gas turbine engine, such as a turbofan engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases. The hot combustion gases flow downstream through turbine stages which extract energy from the hot combustion gases. A fan section supplies air to the compressor.
Combustion gases are discharged from the turbofan engine through a core exhaust nozzle and a quantity of fan air is discharged through an annular fan exhaust nozzle defined at least partially by a nacelle assembly surrounding the core engine. A majority of propulsion thrust is provided by the pressurized fan air which is discharged through the fan exhaust nozzle, while the remaining thrust is provided by the combustion gases discharged through the core exhaust nozzle.
It is known in the field of aircraft gas turbine engines that the performance of a turbofan engine varies during diversified operability conditions experienced by the aircraft. An inlet lip section located at the foremost end of the turbofan nacelle assembly is typically designed to enable operation of the turbofan engine and reduce separation of airflow from the internal and external flow surfaces of the inlet lip section during these diversified conditions. For example, the nacelle assembly requires a “thick” inlet lip section to support operation of the engine during specific flight conditions, such as crosswind conditions, take-off conditions and the like. Disadvantageously, the “thick” inlet lip section may reduce the efficiency of the turbofan engine during normal cruise conditions of the aircraft, for example. As a result, the maximum diameter of the nacelle assembly is approximately 10-20% larger than required during cruise conditions. Since aircraft typically operate in cruise conditions for extended periods, turbofan efficiency gains can lead to substantially reduced fuel burn and emissions.
Accordingly, it is desirable to provide a nacelle assembly having an adaptive structure to improve the performance of a turbofan gas turbine engine during diversified operability conditions.